Membrane Biofilm Reactor (MBfR):
A New Approach to Denitrification
in Wastewater Setting
Ramesh Sharma, Ph.D.
Shane Trussell, Ph.D., P.E.
Trussell Technologies, Inc.
Pasadena, CA
April 2007
Outline
Understanding of the problem
Regulatory aspect
Autotrophs vs. Heterotrophs
MBfR technology overview
State of Art
Previous work
Piloting effort
Understanding of the Problem
The Basics
Regulatory aspects
Drivers for nitrogen removal
Important component of water reclamation and
reuse
Stricter regulations with some locales having ≤
6 mg/L N
Some are talking about ≤ 2 mg/L N
Difficult to go below 10 mg/L N
Enlarging anoxic tanks
Additional electron donor
Both increases cost
Conventional MLE process
Nitrate feed
150-200
mg/L BOD
25-35
mg N/L
Anoxic
10-15 mg N/L
20 mg/L BOD
Aerobic/
nitrification
Return activated sludge
Sludge
Conventional Tertiary
Treatment
Nitrate feed
150-200
mg/L BOD
25-35
mg N/L
Anoxic
10-15 mg N/L
20 mg/L BOD
Post
denitrification
Aerobic/
nitrification
Return activated sludge
Methanol
Sludge
Sludge
Dosing
Issues?
Conventional Tertiary
Treatment
Nitrate feed
150-200
mg/L BOD
25-35
mg N/L
Anoxic
10-15 mg N/L
20 mg/L BOD
Post
denitrification
Aerobic/
nitrification
Return activated sludge
Methanol
Sludge
Sludge
Can we use another approach?
Dosing
Issues?
Autotrophs vs. Heterotrophs
Autotrophic bacteria
Inorganic electron donor
•
•
•
•
Hydrogen gas is electron donor
Inorganic carbon source (CO2 or HCO3No H2 overdosing issue
Low sludge yield (40% less)
Heterotrophic bacteria
Organic electron donor
•
•
•
•
Methanol, acetate etc.
Electron donor for nitrate reduction
Carbon source for cell synthesis
Methanol is toxic to humans
Why so much interest in H2 now?
Efficient delivery system was not available
Low solubility
Flammable (cannot be bubbled)
MBfR overcomes the
limitations of H2 delivery
Diffusion of H2
“Bubbleless” delivery
possible
Hollow fibers
MBfR Technology Overview
State-of-the-Art
MBfRs are not MBRs
MBR = Biological reactor +filter
Provides secondary treatment and
Membrane separates biomass
from the effluent water
MBfRs are not MBRs
MBR = Biological reactor +filter
Membrane separates biomass
from the effluent water
NO3-
MBfR = bubbless
hydrogen gas + biofilm
and hence the name
Membrane biofilm recator
(MBfR)
Biofilm
H2
NO3-
H2
Hollow-fibers a key player
Can be operated at
high pressure without
bubbling H2
Higher gas pressure
inside the tubes
improves H2
availability for the
biofilm
Higher packing of
fibers is possible
Open end for H2 gas
Single fiber
• Smaller foot-print
Sealed end
Counter-diffusion in MBfR:
Membrane-Biofilm Partnership
H2
H2
Counter-diffusion in MBfR:
Membrane-Biofilm Partnership
H2
H2
MBfR opens the door for
Hydrogen
All the advantages with hydrogen fueled
autotrophic denitrifies can be exploited
No overdosing issue
• Low solubility, ~1.2 mg/L at 1 atm
Amount of electron donor needed is less
• Low sludge yield (40% less)
H2 gas is low-cost and non-toxic
MBfR Features
H2 gas diffuses through
the walls across
bubbleless hollow-fiber
H2
membranes
NO3Membrane is the
meeting point for the
nitrate and H2, biofilm
grows on the interface
Nitrate is reduced to
Biofilm
harmless N2 gas
NO3-
H2
Current status of the research
Dr. Rittman and his group invented the technology
Most of the work is in drinking water setting
Partial or full removal of nitrate was possible (Lee and
Rittman 2000, 2002, 2003)
Removal of perchlorate, arsenate, chromate, selenate,
bromate (Nereneberg and Rittman 2002, 2004)
Pilot study for perchlorate and nitrate (Adham et al.,
2003)
Wastewater application is new
Stricter regulation (≤ 1-2 mgN/L vs. 10 mgN/L)
High solids
Piloting effort
Grass Valley WWTP
Lake Arrowhead, CA
~14,000 people
5,106 feet elevation
Treatment Train at GVWWTP
Primary
settling tank
Secondary
settling tank
Trickling Filters
2.3 MGD WWTP
BOD ~ 20 mg/L
Nitrate 8-14 mgN/L
Chlorine
Provides unique opportunity to compare
MBfR and methanol fed denitrification
Methanol
Denitrification tank
MBfR Module
330 micron o.d.
40,000 fibers
Membrane area
42.3 m2
Reactor Volume = 10.5 gal
MBfR Process Schematics
QR = 20 gpm
Two Pilot Units
(long-term and short-term testing)
Long-term
O&M
issues
Short-term
• Loading rates
• HRT
• recycle rate
• Membrane flux
Pilot start-up
• Continuous mode
• 0.15 gpm flow rate
(HRT = 70 min)
• 20 gpm recycle rate
• 15 psi hydrogen gas
• No inoculum was added
Clean fibers at start
Pilot start-up
At start
After 10 days
Pilot start-up (autotrophs accumulate quickly)
18.0
16.0
Influent NO3-N
14.0
12.0
10.0
8.0
Effluent NO3-N
6.0
4.0
2.0
0.0
3/9/07
Effluent NO2-N
3/14/07
3/19/07
Time, days
3/24/07
3/29/07
Current Efforts
Evaluate hydraulic limitation of the system
• Recycle rate, HRT, loading rates, hydrogen pressure
O&M issues and long-term performance
evaluation
Optimization of the MBfR configuration
Membrane material
Fiber diameter
Packing density
Bulk liquid mixing strategy
Compare cost and performance with methanolfed denitrification
Conclusion
MBfR combines biofilm
and H2 gas
Eliminates need for organic C
Over and under-dosing issues
are irrelevant
Less sludge yield
Emerging contaminants removal
Shows promise for low N
• Improved water quality
• decreased cost
O&M issues remain
Acknowledgements
Lake Arrowhead Community Services
District
Ken Nelson, Ryan Gross, Bob Bobik, and
other LACSD staff members
WateReuse Foundation
Applied Process Technology, Inc.
Questions?
[email protected]
Tel # 626-486-0560